Device for guiding a film in an optoelectronic apparatus such as a scanning analyzing device

ABSTRACT

A device for guiding a film in an apparatus comprises guiding and driving means engaged on the two lateral edges of the film. The guiding and driving means is further designed to force the film to follow a curved trajectory in the imaging zone of the apparatus. The means guiding and driving the film include two coaxial rollers whereon the film is urged to span through its two edges, and two parallel driving belts urged respectively to be supported on said edges on the side opposite the rollers, along an arc with predetermined sustaining angle. The invention is useful for guiding film in an optoelectronic apparatus such as a scanning analysis device.

[0001] The present invention relates to a device for guiding a film in an apparatus. It applies in particular, but not exclusively, to guiding a film in an optoelectronic apparatus such as a scanning analyzing device.

[0002] In general, it is known that guiding a film in a viewer raises many problems for the following reasons:

[0003] The film has a convex shape in the unrolled state (curved in a plane perpendicular to its longitudinal axis). Now, it proves to be desirable that, in the zone where the imaging is performed, the film should be straight in the said plane.

[0004] The driving of the film must be consistent over the whole of its width. If this is not the case, the speed of progress will vary from one edge of the film to the other and the film will be driven towards one of its lateral edges, possibly becoming distorted (with risk of jamming).

[0005] The driving at the level of the receiving spools raises problems that are difficult to solve: the speed of progress of the strip is not constant and varies according to the amount of winding on the receiving spool.

[0006] The wear of cylindrical rollers for driving and guiding the film gives rise to a risk of scratching the film by the roller.

[0007] The imaging zone must be formed in a space free of rollers, which increases the dimensions of the apparatus.

[0008] The purpose of the invention is therefore more particularly to eliminate these disadvantages and to solve these problems:

[0009] by presenting a straight portion of film in the imaging zone,

[0010] by driving the film in a consistent manner over the whole of its width with an independent speed of progress,

[0011] by eliminating all risks of damaging the analyzed film.

[0012] For this purpose it proposes a device for guiding the film in an optoelectronic apparatus such as a scanning analyzing device, this device comprising means of guiding and driving engaged on the two lateral edges of the film, these guiding and driving means furthermore being designed in such a way as to force the film to follow a curved trajectory in the imaging zone of the apparatus. By means of these arrangements, the mechanical properties of the film are exploited in order to obtain a straight transverse zone of film in the imaging zone.

[0013] Advantageously, the guiding and driving means of the film will be able to comprise two coaxial rollers upon which the film bears by its two edges and two parallel drive belts respectively bearing on the said edges of the film on the side opposite the one facing the rollers, along an arc of circle of predetermined angle subtended at the center.

[0014] In this way, the guiding and driving are carried out without risk to the film: it is these belts driven by a motor that cause the film to progress at a constant speed and not the rollers as in conventional devices.

[0015] One embodiment of the invention is described below, by way of non-limiting example, with reference to the appended drawings in which:

[0016]FIG. 1 is a side elevation view showing the layout of the constituent components of the device for guiding a film,

[0017]FIG. 2 shows a cross section through AA in FIG. 1,

[0018]FIG. 3 is a partial perspective view of FIG. 1.

[0019] In this example, the structure of the device comprises two parallel metal plates la, lb separated by three cross-pieces 2 a, 2 b, 2 c disposed along the upper side of the plates. These various components form a rigid constituent assembly of the device for guiding the film 3. The distance separating the two metal plates 1 a, 1 b is slightly greater than the width of the film 3 to be analyzed.

[0020] According to the invention, the device comprises means of guiding, driving and winding the film and a device for detecting the presence of the film.

[0021] The device for guiding the film 3 comprises in an imaging zone two parallel coaxial rollers, one of which is shown 4 a, mounted such that they rotate by means of ball bearings and held by backing plates, of which two are shown, 5 a, 6 a. The lateral edges of the film 3 respectively bear on these two rollers along an arc of circle in such a way that the film follows a circular trajectory. Thus, along this circular trajectory, it exhibits a cylindrical shape with a straight generatrix. This position makes it possible to obtain in the imaging zone a straight transverse zone perpendicular to which is disposed a slot formed in a panel 7 integral with the two plates 1 a, 1 b and forming a rectangular space for conveying light rays passing through the film..

[0022] The device for driving the film 3 comprises two parallel belts 8 a which move in synchronism and which respectively bear on the lateral edges of the film 3 at the level of the circular trajectory. In this way, a friction drive on the two lateral edges of the film is obtained, which eliminates any possibility of variation of speed between these two edges. The two belts, only one of which is shown, 8 a, have notches in the side facing away from the film 3, the driving of the belts being carried out by means of two coaxial notched pulleys 9 a and 9 b whose common shaft 10 is driven by an electric motor 11 and two free notched pulleys, only one of which is shown, 12 a. The tension and positioning of these two belts 8 a, 8 b are provided by rollers, only one set of which is shown, 13 a, 13 b, 13 c.

[0023] The device for winding the film 3 consists of a diabolo-shaped roller 15 mounted such that it rotates about a spindle 16 parallel with the axes of the rollers with spring return. This spindle is guided in such a way as to be able to move along an oblong opening 17 in such a way as to move according to the thickness of the winding of the film 3 on the roller 15. The major axis of the oblong opening 17 is oriented perpendicularly with respect to the tangential plane of application of the belts on the edges of the film (application force collinear with the major axis of the oblong hole 17). Two pairs of arms, only one of which is shown, 18 a, 19 a, guide the film during its introduction onto or extraction from the diabolo-shaped roller 15. The arms are hinged. It should be noted that the angular velocity of the diabolo, the latter not having any driving means of its own, depends on the amount of winding of the film 3.

[0024] The zone of introduction of the film comprises a device for detecting the presence of the film 3 comprising a light generator 20/light receiver 21 pair. 

1. A device for guiding a film, comprising means of guiding and driving engaged on two lateral edges of the film, these guiding and driving means furthermore being designed in such a way as to force the film to follow a curved trajectory in an imaging zone of an optoelectronic apparatus, and said guiding and driving means comprise two coaxial and mutually independent rollers, upon which the film bears by its two lateral edges, and two parallel drive belts respectively bearing on the said edges on a side opposite one facing the rollers, along an arc of circle of predetermined angle subtended at a center.
 2. The device as claimed in claim 1, further comprising two parallel plates.
 3. The device as claimed in claim 2, wherein said plates are separated by cross-pieces.
 4. The device as claimed in claim 1, wherein said coaxial rollers are parallel and mounted such that they rotate.
 5. The device as claimed in claim 1, wherein light rays are conveyed to said imaging zone through a slot formed in a panel integral with said plates.
 6. The device a claimed in claim 1, wherein said belts have means for causing the belts to move in a synchronous manner.
 7. The device as claimed in claim 6, wherein said belts have notches on a side opposite to the one facing the film.
 8. The device as claimed in claim 7, wherein said belts are driven by two coaxial notched pulleys driven by a motor.
 9. The device as claimed in claim 7, wherein tension and positioning of the said belts are provided by rollers.
 10. The device as claimed in claim 1, further including winding means comprising a diabolo-shaped roller mounted such that the diabolo-shaped roller rotates.
 11. The device as claimed in claim 10, wherein said diabolo-shaped roller comprises means of movement which depend on a thickness of a winding of the film.
 12. The device as claimed in claim 1, further comprising a device for detecting presence of the film. 